1. Field of the Invention
The invention disclosed herein relates generally to the field of paper handling preparation and more particularly, to a stacking apparatus.
2. Background of the Invention
Mailpiece stacking devices are known for taking singulated items and forming them into stacks or columns. Stackers are commonly used in conjunction with photocopier machines, printers, facsimile machines, mailing machines, folders, folder/sealers, small envelope inserter devices, mail openers, envelope printers and labelers. In many of these applications, such as mailing machines and envelope printers, an envelope is imprinted with an address and then immediately fed into a stacker. The ink on the envelope is often not dry as the mailpiece enters the stacker. Failure of the ink to dry enables a successive envelope to smear the ink on a previous envelope in the stacker.
In order to obtain the postal rate discounts, the order of the mailpieces that have been presorted and processed by the mail-processing machine in consecutive order needs to be maintained. The removed stack of mailpieces can be manually placed in a mail tray that is sent to the postal service. In this manner, the user can take advantage of lower postal rates that are provided to users who tray envelopes according to predetermined criteria. The predetermined criteria includes the maintaining of mailpieces in the exact order in which they were processed in the mail processing machine. Generally, the predetermined criteria relates to a reduction in the postal service""s handling of the mail from the mailers. The United States Postal Service (xe2x80x9cUSPSxe2x80x9d) offers several levels of discounts to mailers. The level of discount typically is based on the number of criteria met by the mailer. For example, in order to maximize such postage discounts, the USPS requires that high volume mailers presort the mailpieces, apply a ZIP+4 bar code to each mailpiece, and package their mail into trays with each tray tagged in accordance with the Domestic Mail Manual.
The instant invention relates to a method and apparatus for stacking documents to either the top or the bottom of the stack. Users of mailing machines, inserting equipment or other mail preparation devices often would like the flexibility of being able to add mailpieces to the bottom or the top of a mailpiece stack. Thus, some mail processing systems prefer top stacking in some applications and bottom stacking in other applications. For example mailing machine systems having bottom feeder for which top stacking is preferred in order to keep the mailpieces in their original order. Another example is an addressing system configured to print addresses from multiple data bases. Some of the databases may list the addresses in forward order, while others may list addresses in reverse order. It is generally preferred to stack the mailpieces in forward order. A system such as the present invention, with selectable top or bottom stacking, could accomplish this modification the database.
Another example of a system which could benefit from an output device which can selectably stack either on top or on the bottom of the stack is a meter/mailing machine combination capable of handling mixed sizes of mailpieces and selectably sealing the mail or not sealing it during the franking operation. Pitney Bowesxe2x80x9d Paragon(copyright) and DM950(trademark) are examples of such a system. Bottom stacking may be preferred when processing a consistently sized batch of mailpieces which need to be sealed. Since the weight of the stack is felt by the new mailpiece added to the bottom and the weight assists in sealing the new mailpiece as well as other mailpieces in the stack. Additionally, when the mailpieces have glossy surfaces (and are thus more prone to image smearing during the stacking operation than regular mailpieces), the customer may prefer bottom stacking to minimize the probability of image smearing. Top stacking may be preferred for mailpieces that have already been sealed, or for jobs having intermixed mailpiece sizes, in which case top stacking may be the only option which will handle the stacking function.
An additional problem with the prior art is that the stackers typically have large space requirements, for example power stackers typically have a long run length. For some customers, the relatively large space requirements for the stacker can inhibit sales and placements of the product.
Additional difficulty with the prior art is that vertical top stacking operations can create untidy stacking. This is because mailpieces drop a long distance to the top of the stack and often do not settle neatly on top of the stack. Some mailpieces settle on edge, or sometimes flip over, or the mailpieces end up sticking partially out of the stack. In general, the stacking operation requires operator vigilance and frequent unloading or manual tidying the stack to insure continuous operation.
Thus, one of the problems of the prior art is that an ink from an envelope can smear onto an adjacent envelope. Another problem is that it is desirable to maintain the ordered of the mailpieces being stacked. Another problem of the prior art is untidy stacking. Another problem of the prior art is the need for a large footprint. Another problem of the prior art is unavailability of selecting stacking sequence (via top or bottom). Therefore, a system and method for stacking envelopes is needed which provides decreased smearing, maintains mailpiece order, provides tidy stacking, provides a smaller footprint and allows operator selectability of stacking sequence.
This invention overcomes the disadvantages of the prior art by providing an apparatus and method for stacking mailpieces. In particular, an embodiment of the present invention is an operator selectable top or bottom stacking apparatus that arrays the stack of mailpieces in a vertical orientation, increases the stacker capacity while reducing the footprint, and improves the tidiness of the stacking when either the top or bottom stacking feature has been selected. The bottom stacking feature of this invention reduces sliding contact with other mailpieces or portions of the stacker mechanism for portions of the mailpiece that are likely to be recently imaged, thus reducing the possibility of smeared images. It enhances sealing since recently stacked mailpieces feel the weight of the stack. And it enables simple unload while running capability without operator skill and without shutting down the system in the middle of a job. The top stacking feature adds further benefits such as enabling stacking of mixed mail sizes, and it improving the tidiness and reliability of the top stacking function by maintaining a preferred minimum dropping distances for mailpieces added to the top of the stack.
An embodiment of the present invention comprises an apparatus for stacking mailpieces in a vertical stack. The apparatus includes a means for holding the stack in a tilted position, the means comprising a tilted base. A sliding retainer is positioned to support a side of the stack that is tilted toward the sliding retainer by the means for holding the stack in a tilted position. A first input area is positioned above retainer element and a second input area is positioned below the retainer element and above the means for holding the stack in a tilted position. A translating carriage means is attached to the means for holding the stack in a tilted position, the translating carriage means is movable in an approximately or about vertical direction in response to a control signal indicating the direction of about vertical movement; whereby the apparatus is configured to selectably add mailpieces to the top of the vertical stack via the first input area or the bottom of the vertical stack via the second input area. It is further contemplated that the apparatus may be tilted a predetermined magnitude.
In another embodiment, the present invention comprises a method of stacking mailpieces in a vertical stack, the method comprising: a) providing a means for holding the stack in a tilted position; b) delivering mailpieces to the top of the stack; c) detecting whether the top of the stack has reached a predetermined height; d) lowering incrementally the means for holding the stack in a tilted position to a predetermined position that will provide the means for holding the stack in a tilted position space to accept additional mailpieces. The method further comprises e) detecting whether the top of the stack has reached another predetermined height indicating that a portion of the stack has been removed from the means for holding the stack in a tilted position; and f) raising the means for holding the stack in a tilted position to a predetermined position that provides a preferred dropping distance for mailpieces that are added to the stack.
An advantage of the present invention is that it decreases image smearing, reduces stacker footprint, improves sealing, provides ordered stacking regardless of the order of the input of the elements, such as, for example, mailpieces (i.e., stacks in 1 to N order), an operator selectable top or bottom stacking apparatus that arrays the stack of mailpieces in a vertical orientation, improves the tidiness of the stacking when either the top or bottom stacking feature has been selected, enables simple unload while running capability and could be unloaded during the processing of a job, and, without shutting down the system in the middle of a job, enables stacking of mixed mail sizes, and it improves the tidiness and reliability of the top stacking function by maintaining a preferred minimum dropping distances for mailpieces added to the top of the stack. Other advantages of the invention will in part be obvious and will in part be apparent from the specification. The aforementioned advantages are illustrative of the advantages of the present invention.